The Patch Antenna For DJI Cendence Remote Controller

Since receiving the DJI Cendence I have seen questions time and time again asking is it worth using the DJI Patch antenna compared to the standard omnidirectional sticks and what benefit does the patch antenna bring.  Because of this I decided to do some tests to try and show the difference between them and see what was actually better as well as get some data on how directive the patch is in use too.

A Closer Look at the Patch

Since receiving the DJI Cendence I have seen the question time and time again asking is it worth using the DJI Patch antenna compared to the standard omnidirectional sticks and what benefit does the patch antenna give. Because of this I decided to do some tests to try and show the difference between them and see what was one was actually better to use as well as get some data on how directive the patch is as well.

Originally when this released there was no indication of it being connected or working, the recent Cendence firmware V02.00.0090 changes this and now shows when it is connected and working via the status bar on the bottom of the main screen, you should see the below message as well getting a beep when you plug it in as long as its updated.

Something else to be aware of is if your not getting this connected message even after updating the firmware you may have a faulty patch unit and I would suggest opening a ticket with DJI Support and get it repaired if that is the case.

The Test Setup

The first issue I had was finding a way to test the antenna performance differences as its actually quite difficult to do while getting reliable results and not actually breaking any distance laws, in the end I chose to set the Inspire 2 up in a fixed position sitting on a table just over 500m the other side of a field with clear LOS. The reason I choose this method over actually flying was I wanted to be able to swap the antennas quickly without triggering RTH and also have a fixed set of conditions to try both types of antenna.

While 500m may not sound a lot to test this there was an valid reason for choosing this distance as I wanted to specifically use the 1080P live feed mode on the Inspire 2. This higher resolution live feed generally give a lot less signal range over the standard 720P live feed and most of the time your not able to get much more than a few hundred meters in this mode so it is ideal to demonstrate the difference in antenna performance.

The Patch Directivity

I started the tests with the patch antenna fitted and I first wanted to look at the patch antennas directivity in the horizontal axis, once connected to the craft I started to rotate and it was clear the patch has a very noticeable window of 60 degrees each side of centre before the signal drops, when testing and moving the signal remained at almost 100% right up to the point of loss then it dropped off a cliff, I tested this multiple times with my phone measuring angle and it was almost 60 degrees perfect each side off centre every time.

Next I tested this in the vertical axis and this was a little more forgiving, I tested with the aircraft flying above as well as with it on the table and while it appears the 60 degrees angle stands here too but I was able to stay connected more than I could in the horizontal towards the edge of the antennas field of view.

Signal Tests Patch Vs Omni Sticks

For the first signal tests I started with the patch antenna fitted with the live feed set to 1080P, I was able to get a solid full signal in all bitrates all the way up to the maximum of 10mbps in Go 4. As long as I stayed within the 60 degrees FOV of the antenna the signal remained solid and live feed was perfect with little to no breakup or drops or latency increases at all.

Next I swapped to the DJI omnidirectional stick antennas and set them in the recommended vertical rabbit ears positions, starting in 1080P at 10mbps I was not able to get a connection at all, I tried moving closer to the craft and only once I got roughly 300m away did the connection come back but it was totally unusable, at the 500m mark it was a total black out, no signal at all

Back at the 500m mark I dropped the bitrate down to 8mbps and this time it would actually connect to the craft but the feed was totally unusable, blocking and not able to hold a good connection, I was getting constant breakup and delay and it was not usable for a live feed and not something I would be happy flying with.

Dropping it to 6mbps made the connection fairly solid however there was more latency than I was getting on the patch antenna and I would normally get and any cameras movements causes blocking and the image to tear and break up, while it was usable at this point it was not ideal. Only when setting it to 4mbps was I able to get a solid connection that was similar to the patch antenna or what I would expect in normal use, after testing for several hours It was clear anything above this with the omni sticks and things stated to fall off and degrade badly.

Conclusion

I did these tests over several hours on multiple channels and it was very clear to me that the patch antenna in this situation was providing a much more stable signal in 1080P mode at the higher bitrates especially, while these tests are not perfect or 100% definitive am i’m absolutely sure that the patch antenna does give a big benefit over the omnidirectional sticks when your able to stay with in the field of view of the patch.

All of these tests were conducted in the 1080P live feed mode and I know this is something most users may not be using regularly however the results should directly translate over to the usual 720p live feed mode as well,  as with all these thing thats not to say its going to result in a doubling of the signal range or even any increase  when flying but I do believe the patch antenna will give better more stable live feed link overall.

One thing for sure is if your looking to use the Inspire 2 in a broadcast situation with 1080P live feed or if  you just want the most stable link you can get then in my opinion you want to the use the patch antenna on the Cendence if you can, in these tests it allowed me to get to the full 10mbps data rate without issue and in all the time I have been using it oI have always had no reason to doubt it

Very informative, as usual. Yet, the issue of patch antenna advantages when attempting long distance transmission with average 720p/4Mbsec setting remains to be field confirmed. To my experience there's none, but my antenna - although recognized by Cendence - wasn't plugged in during FW update. I didn't find any way to update patch antenna FW after the fact, other than sending to DJI for fix.

Matthew Dobrski Posted at 2018-6-17 11:23
Very informative, as usual. Yet, the issue of patch antenna advantages when attempting long distance transmission with average 720p/4Mbsec setting remains to be field confirmed. To my experience there's none, but my antenna - although recognized by Cendence - wasn't plugged in during FW update. I didn't find any way to update patch antenna FW after the fact, other than sending to DJI for fix.

Updated to sort the mess out I posted, should be better now

Thanks, I think its harder to show this at range for a number of reasons but I do think it will give a more solid connection overall even at 720P but i'm not gin got say it will increase range as there is a point with the cliff is there regardless.

Excellent review, very helpful. Thanks!

Ken

Mad_Angler1 Posted at 2018-6-17 11:27
Updated to sort the mess out I posted, should be better now

Thanks, I think its harder to show this at range for a number of reasons but I do think it will give a more solid connection overall even at 720P but i'm not gin got say it will increase range as there is a point with the cliff is there regardless.

Thank you for clarification, Mad Angler. Well, than I'll have to wait for Tracktenna to become available, assuming that this idea is still alive at DJI. Not that I want to challenge distance records with Cendence, but  farther flights are part of my landscape photography with M200 drone.
Oh,BTW: I've noticed rather unusal V positioning of omni antennas on your Cendence. Did you find this more efficient than straight up in parallel?

Cheers,
Matthew.

Excellent instruction and review - what an amazing bit of kit!

Matthew Dobrski Posted at 2018-6-17 15:25
Thank you for clarification, Mad Angler. Well, than I'll have to wait for Tracktenna to become available, assuming that this idea is still alive at DJI. Not that I want to challenge distance records with Cendence, but  farther flights are part of my landscape photography with M200 drone.
Oh,BTW: I've noticed rather unusal V positioning of omni antennas on your Cendence. Did you find this more efficient than straight up in parallel?

The Rabbit ears or V is the optimal setup for omni sticks when in flight as it allow for craft angle, while actually on the deck I probably should have got for vertical its not going to make any difference, one of my preferred setup for the Cendence with the omni directional sticks is actually fully down as it helps them to clear the bark of the crystalsky and give better angle.

As long as they remain in the vertical plane being up or down does not make a difference and having a slight angle on them will improve reception when the craft is moving in the air.

Mad_Angler1 Posted at 2018-8-6 00:28
The Rabbit ears or V is the optimal setup for omni sticks when in flight as it allow for craft angle, while actually on the deck I probably should have got for vertical its not going to make any difference, one of my preferred setup for the Cendence with the omni directional sticks is actually fully down as it helps them to clear the bark of the crystalsky and give better angle.

As long as they remain in the vertical plane being up or down does not make a difference and having a slight angle on them will improve reception when the craft is moving in the air.

Oh, ears down ... great idea, never crossed my mind! BTW, just recently performed transmission range test with both antennas ( https://forum.dji.com/forum.php? ... D427%26typeid%3D427 ) ... Not bad, not bad at all ...

Cheers.

Confusing when the Stated specs of the Cendence with omni is (FCC) 26 dbm & 28 dbm respectively then i noticed these stated specs for the Patch Antenna

Compatibility        Cendence Remote Controller
Half Power Beamwidth (HPBW)        60° (2.4 GHz)
                                                                30° (5.8 GHz)
Antenna Gain        8 dBi (2.4 GHz)
                              10 dBi (5.8 GHz)

Are these additional Gains on top of stated and do we know at what power?  FCC limit i thought was 36 dbm overall.
Interesting "rules" quote:

"Maximum Effective Isotropic Radiated Power (EIRP) is 36 dBm (4 watt). ... The maximum EIRP allowed is 53 dBm (30 dBm plus 23 dBi of antenna gain). In the 2.4 GHz band you can increase the antenna gain to get an EIRP above 36 dBm but for every 3dBi increase of antenna gain you must reduce the transmit power by 1 dBm"

All very nice but... the Patch Antenna was mounted incorrectly! The small rubber feet must face down and serve as a support when the antenna is folded, in the photos of this test it is the opposite therefore the directionality of the signal is compromised (and also the whole test).
...or is another version without rubber feet?

https://store.dji.com/product/cendence-patch-antenna

as you can see direct from the DJI manual the patch antenna should have the CANBUS wire on the side next to the SDI port on the rear. The OPs connection is correct.

i think the OP had an early prototype model which may explain the missing feet.

The middle wire in that diagram, I dont know what its called, but not the 2 antenna wires, is there any way to have that replaced on its own or do you require a whole new patch antenna?

My one got bent when I placed it on the ground and the controller rolled backwards onto it.

I have been using the standard pair of antenna (2 aerials) that came in the box since, and being honest, I have found them to be better than the patch antenna - but i would still like to get it fixed.

guess it depends on how we operate  the aircraft. ive used the aerials on the I1 but since the patch came out for the I2, thats all ive used and its been flawless for me. im more a ground camera operator but I do use the I2 on occasion and never had an issue with the patch.

if you mean the canbus connector on the patch? if you're handy with wiring maybe you can replace it but i doubt DJI will sell you just that one part. you may find one second hand for cheap as some people out there may be like you and also not like to use the patch...